diff --git a/lib/delete-merged-branch.js b/lib/delete-merged-branch.js
index 59b5817..1f4a368 100644
--- a/lib/delete-merged-branch.js
+++ b/lib/delete-merged-branch.js
@@ -3,13 +3,15 @@ const shouldClosePrByDefault = () => {
 }
 
 module.exports = async (context) => {
-  const config = await context.config('delete-merged-branch-config.yml', { exclude: [], delete_closed_pr: shouldClosePrByDefault() })
+  const config = await context.config('delete-merged-branch-config.yml', { exclude: [], on_base: [], delete_closed_pr: shouldClosePrByDefault() })
   const headRepoId = context.payload.pull_request.head.repo.id
   const baseRepoId = context.payload.pull_request.base.repo.id
 
   const owner = context.payload.repository.owner.login
   const repo = context.payload.repository.name
   const branchName = context.payload.pull_request.head.ref
+  const baseBranchName = context.payload.pull_request.base.ref
+
   const ref = `heads/${branchName}`
 
   if (headRepoId !== baseRepoId) {
@@ -17,6 +19,12 @@ module.exports = async (context) => {
     return
   }
 
+  if (config.on_base && config.on_base.length > 0 &&
+      !config.on_base.some((rule) => new RegExp(`^${rule.split('*').join('.*')}$`).test(baseBranchName))) {
+    context.log.info(`Base does not match any 'on_base'. Keeping ${context.payload.pull_request.head.label}`)
+    return
+  }
+
   if (config.exclude.some((rule) => new RegExp(`^${rule.split('*').join('.*')}$`).test(branchName))) {
     context.log.info(`Branch ${branchName} excluded. Keeping ${context.payload.pull_request.head.label}`)
     return
diff --git a/test/lib/delete-merged-branch.test.js b/test/lib/delete-merged-branch.test.js
index 73addbf..c6f0adf 100644
--- a/test/lib/delete-merged-branch.test.js
+++ b/test/lib/delete-merged-branch.test.js
@@ -82,13 +82,41 @@ describe('deleteMergedBranch function', () => {
     })
   })
 
-  describe('branch is merged', () => {
+  describe('base not included in config', () => {
+    it('should log it didn\'t delete the branch', async () => {
+      context.config = jest.fn().mockReturnValue({
+        exclude: [],
+        on_base: ['something', 'other', 'than', 'the', 'base', 'branch']
+      })
+      context.payload.pull_request.head.label = 'foo:bar'
+      await deleteMergedBranch(context)
+      expect(context.log.info).toBeCalledWith(`Base does not match any 'on_base'. Keeping ${context.payload.pull_request.head.label}`)
+    })
+
+    it('should NOT call the deleteReference method', async () => {
+      context.config = jest.fn().mockReturnValue({
+        exclude: [],
+        on_base: ['something', 'other', 'than', 'the', 'base', 'branch']
+      })
+      context.payload.pull_request.head.label = 'foo:bar'
+      await deleteMergedBranch(context)
+      expect(context.github.git.deleteRef).not.toHaveBeenCalled()
+    })
+  })
+
+  describe.each([
+    false,
+    true
+  ])('branch is merged', (baseExplicitlyIncluded) => {
     beforeEach(async () => {
       context.payload.pull_request.merged = true
+      if (baseExplicitlyIncluded) {
+        context.config.on_base = [context.payload.pull_request.base.ref]
+      }
       await deleteMergedBranch(context)
     })
 
-    it('should call the deleteReference method', () => {
+    it('should call the deleteReference method, base in on_base: ' + baseExplicitlyIncluded, () => {
       expect(context.github.git.deleteRef).toHaveBeenCalledWith({
         owner,
         ref: `heads/${ref}`,
@@ -96,11 +124,11 @@ describe('deleteMergedBranch function', () => {
       })
     })
 
-    it('should log the delete', () => {
+    it('should log the delete, base in on_base: ' + baseExplicitlyIncluded, () => {
       expect(context.log.info).toBeCalledWith(`Successfully deleted ${owner}/${repo}/heads/${ref} which was merged`)
     })
 
-    describe('deleteReference call fails', () => {
+    describe('deleteReference call fails, base in on_base: ' + baseExplicitlyIncluded, () => {
       beforeEach(async () => {
         context.github.git.deleteRef = ''
       })